Printed circuit card

Abstract

A printed circuit card made of plastic has a carbonization sensor for protection against smoldering electrical fires. The carbonization sensor contains a first and a second conductor track disposed on the printed circuit card and also a monitoring device. The two conductor tracks are electrically insulated from one another by the plastic, and the monitoring device monitors an insulating state of the two conductor tracks in relation to one another and produces a fault signal. Local overheating of the printed circuit card is detected at an early time by the carbonization sensor, before an avalanche effect caused by the carbonization, which makes the printed circuit card electrically conductive, leads to a smoldering electrical fire.

Description

BACKGROUND OF THE INVENTIONField of the Invention[0001]The invention relates to a printed circuit card made of plastic having protection against smoldering electrical fires.[0002]The printed circuit card, i.e. an insulating element for supporting electronic components and conductor tracks, generally is formed of plastic. Because of the heat that is introduced during soldering operations, the plastic is, in particular, a thermosetting plastic. Usually, an epoxy resin reinforced with glass fibers is used.[0003]In many electrical or electronic circuits, a defective electronic component causes the risk of fire or smoke developing. In particular with component loading techniques (adhesive bonding, SMD), an electronic component is no longer kept away from the printed circuit card by legs, but instead lies directly on it. A consequence of this is that a defective, overheating component causes a great amount of heat to be introduced into the printed circuit card.[0004]As from a certain temp...

AI Technical Summary

Benefits of technology

[0007]It is accordingly an object of the invention to provide a printed circuit card which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which has reliable and rapid protection against smoldering electrical fires. A smoldering fire is to be detected quickly enough that the printed circuit card concerned can be disconnected from the electrical supply before electrically caused smoke becomes hazardous. The avalanche effect is to be prevented at an early time.

Problems solved by technology

If the development of heat of a defective component leads to increased heat being introduced into the printed circuit card, and thereby to carbonization, at this point the insulating property of the printed circuit card is lost.

This happens long before the occurrence of flames over a large area of the printed circuit card leads to a detectable amount of smoke and toxic fumes.

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